1. Field of the Invention
This invention relates to a bearing blanket which extends through an extended nip defined by a shoe and a cooperating backing roll for pressing water from a formed web.
More particularly, the present invention relates to a bearing blanket including a woven-base fabric and a liquid impervious urethane layer applied to the base fabric.
2. Information Disclosure Statement
Bearing blankets are used for pressing water from a formed web during passage of the web through an extended nip press.
An extended nip press includes a press shoe and a cooperating backing roll for defining therebetween an extended nip. The press shoe defines a concave surface which cooperates with the outer surface of the backing roll such that when an endless looped bearing blanket extends through the extended nip, the bearing blanket is permitted to move with a web supported thereon through the extended nip. The interface between the bearing blanket and the shoe is lubricated to permit relative movement therebetween and the blanket together with one or more felts supports the web during transit of the web through the extended nip.
In the prior art, bearing blankets have been typically manufactured by training a base fabric around spaced rollers and applying a first coating of urethane to one side of the base fabric.
The urethane coating is then cured and optionally grooved. The base fabric with the first coating is subsequently turned inside out so that the other side of the base fabric can be coated.
Not only is the aforementioned manufacturing process relatively time consuming and complex, but more particularly, such prior art proposals have resulted in a bearing blanket having two urethane layers thereon with the attendant thickness thereof.
Such undue thickness and the provision of two such layers has resulted in the delamination of the urethane layers under extended usage of the bearing blanket.
Additionally, reversing of the bearing blanket in order to coat the opposite side of the base fabric has proved cumbersome. Problems have been experienced when manufacturing a bearing blanket suitable for use in the so-called apple type ENP disclosed in U.S. Pat. No. RE31,923 to Justus. A blanket of the aforementioned type typically has a circumference of 13 feet and a width of up to 35 feet. Turning such a blanket inside out without damaging the urethane layer applied thereon has proved to be difficult.
The present invention overcomes the aforementioned inadequacies of the prior art proposals by applying a single layer of urethane to a base fabric such that the urethane penetrates into and through the base fabric to provide a smooth shoe contacting face and a subsequently grooved web face.
Such single layered bearing blanket has a thickness which is substantially less than the thickness of the double layered prior art proposals and does not require the reversing step during manufacture thereof.
Therefore, it is the primary object of the present invention to provide a bearing blanket that overcomes the aforementioned inadequacies of the prior art proposal and which makes a significant contribution of the art of extended nip pressing.
Another object of the present invention is the provision of a bearing blanket having a single urethane layer so that the thickness of the blanket is minimized thereby inhibiting delamination of the resultant blanket.
Another object of the present invention is the provision of a bearing blanket in which a single layer of urethane is applied to a base fabric such that reversing of the blanket during manufacture thereof is avoided.
Another object of the present invention is the provision of a bearing blanket in which the web face is provided with a plurality of parallel-spaced grooves with grooves adjacent to the lateral edges of the blanket being ground-off in order to relieve the stresses applied to the blanket during multi-plane bending of the blanket while extending through an extended nip.
Other objects and advantages of the present invention will be apparent to those skilled in the art by consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings.